MORPHOLOGICAL DEVELOPMENT OF THE OPERCULAR APPARATUS IN KNERIA-WITTEI(OSTARIOPHYSI, GONORYNCHIFORMES) WITH COMMENTS ON ITS POSSIBLE FUNCTION

The structure, development and function of the male opercular apparatu s were examined in the freshwater ostariophysan Kneria wittei using a combination of techniques (i.e. histology, SEM, skeletal clearing and staining). Specimens ranged in standard length from 10 to 65 mm. Morph ological comparisons were also made between males and females, as well as comparisons with closely related taxa. Our study shows that the Kn eria opercular apparatus consists of two structures: an opercular cup and a posteriorly positioned opercular flange, each of which is compos ed largely of connective tissue with keratinized papillae and ridges p ositioned on the surface. Our results further show that the developmen t of the opercular apparatus is linked directly to the development of the anterior vertebral elements (i.e. epicentral intermuscular bones a nd neural arches). Understanding the function of the opercular apparat us must therefore include an understanding of its associated skeletal elements. As a result of our morphological observations two hypotheses for the function of the opercular unit are addressed; as an auditory specialization, and as an adhesive device. (C) 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.